Oil pump for enclosed motor-compressor,especially for small refrigerating machines

ABSTRACT

AN ENCAPSULATED REFRIGERATION MOTOR-COMPRESSOR HERMETICALLY SEALED IN A CAPSULE AND IN WHICH THE MOTOR HAS A VERTICALLY DISPOSED HOLLOW MOTOR SHAFT WHICH IS ATTACHED A LENGTH OF TUBING IN COMMUNICATION WITH THE BORE OF THE SHAFT DEFINING A FIRST CENTRIFUGAL OIL PUMP. A SECOND LENGTH OF TUBING IS MOUNTED CIRCUNFERENTIALLY AND AXIALLY OF THE FIRST-MENTIONED LENGTH OF TUBING SPEED   OUTWARDLY THEREFROM DEFINING A SECOND CENTRIFUGAL OIL PUMP DRIVE IN CONJUNCTION WITH THE FIRST PUMP FROM THE COMMON MOTOR SHAFT.

Feb. 2, 1971 v, VALBJORN E'TAL 3,560,117

on. PUMP FOR ENCLOSED MOTOR-COMPRESSOR, ESPECIALLY FOR SMALL REFRIGERATING MACHINES Filed Jan. 30, 1969 INVENTORIIT Knud V. Valbjorn Hans U. Leffers Heinz Mahncke United States Patent 3,560,117 OIL PUMP FOR ENCLOSED MOTOR-COMPRESSOR, ESPECIALLY FOR SMALL REFRIGERATING MACHINES Knud V. Valbjorn, Nordborg, and Hans Ulrik Lelfers and Heinz Mahncke, Sonderborg, Denmark, assignors to Danfoss A/S, Nordborg, Denmark, a company of Denmark Filed Jan. 30, 1969, Ser. No. 795,301 Claims priority, application Germany, Feb. 1, 1968, P 16 28 156.4 Int. Cl. F04b 39/02 US. Cl. 417372 8 Claims ABSTRACT OF THE DISCLOSURE An encapsulated refrigeration motor-compressor hermetically sealed in a capsule and in which the motor has a vertically disposed hollow motor shaft to which is attached a length of tubing in communication with the bore of the shaft defining a first centrifugal oil pump. A second length of tubing is mounted circumferentially and axially of the first-mentioned length of tubing spaced outwardly therefrom defining a second centrifugal oil pump driven in conjunction with the first pump from the common motor shaft.

This invention relates generally to hermetic motorcompressor units and particularly to a new and improved oil pump for small refrigeration motor-compressor units.

Motor-compressor units, for example refrigeration compressors, are known in which the motor shaft has an axial bore and is mounted vertically. A centrifugal pump is mounted on the vertical shaft constructed as a tubular element extending downwardly into the oil in an oil sump formed within the hermetic capsule. These pumps are simple to construct and have given excellent service in operation; however, their oil output capacity is generally too small.

It is an object of the present invention to provide an improved centrifugal pump for motor-compressor units of the type above described which is simply constructed, has a greater output capacity than the known similarly constructed centrifugal pumps.

In a motor-compressor unit according to the invention, the motor shaft is disposed vertically within a capsule and has an axial bore through which oil is delivered to the unit from a first centrifugal pump defined by a first length of tubing connected to the shaft for rotation thereing axially of the first length of tube and spaced therefrom defining a second pump suction.

The second length of tubing is mounted on the first length of tubing by radially inwardly extending depressions defining projections extending into the second length of tubing and bearing against the outer periphery of the first length of tubing for fixing the second pump on the first centrifugal pump.

Since the second length of tubing has a greater inner diameter than the first length of tubing, it produces a greater centrifugal force when driven by the motor shaft common to both sumps so that a large volume of oil is delivered through the inner or first length of tubing and a large volume is delivered outwardly thereof in the space formed between the two tubes. The two oil flows can therefore be either combined or maintained separately for lubricating specific hearings or portions of the unit "ice independently of each other. Moreover, one stream can be used for lubrication and the other flow can be used for cooling the unit.

The second length of tubing has an outwardly flaring collar at the top thereof whereby it bears against a shortcircuiting ring of the motor-rotor thereby defining a fluidtight annular chamber between the collar and the shortcircuiting ring. This chamber is in communication with the space between the two tubes and is in communication with axially extending passages which extend upwardly in or on the rotor so that the axial bore in the motor shaft is available for usual cooling and lubricating purposes while oil supplied through the above-mentioned rotor passages can be used for cooling the motor itself.

In a preferred embodiment, oil from the second centrifugal pump is used for cooling the coil ends of the motor while bearing lubrication takes place by the oil flow through the axial bore of the motor shaft. In this way, a fairly large quantity of oil is available for delivery over the motor coils so that the motor heat is dissipated without the oil undergoing any great increase in temperature.

Preferably, the inner or first length of tubing has a conical lower end portion or element extending downwardly into the oil sump a greater length beyond a lower conical end portion or element of the second or outer length of tubing defined in the second centrifugal pump. In this way suction through the first length of tubing is not interfered with by the outer second length of tubing. Nevertheless, the output capacity of the second pump is not adversely affected since, as a result of its greater diameter, it generates a greater effective centrifugal force than the inner pump and the outer surfaces of the lower conical end portion of the first length of tubing or inner pump delivers oil into the space or chamber between the two lengths of tubings.

Other features and advantages of the motor-compressor unit and oil pump in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawing in which the single figure is an axial section of a hermetically sealed motor-compressor unit constituting a small refrigeration compressor.

As illustrated in the drawing, a motor-compressor unit according to the invention comprises a hermetic capsule 1 in which is resiliently suspended, by a suspension system not shown, a refrigeration machine constituting a compressor having a downwardly extending portion 2 which supports a stator 3 of an electric drive motor and defines a bearing 4 for a shaft 5 of the motor. Upward extensions 6 on the motor support 2 form noise-reducing or absorbing chambers 7 of the compressor and a cylinder having an axis perpendicular to the plane of the drawing. An insert member 8, inserted into a central space defined by the extensions 6, seals or closes off the noisereducing chambers 7 and forms or defines a second bearing 9 for the motor shaft. A support plate .11 supports the shaft vertically and a centrifuging disc 12 fixed to the rotatably driven shaft by a bolt 10, as illustrated.

The shaft 5 carries on a crank 13 a crank bearing 14 to which is connected a connecting rod of a compressor piston, not shown. The motor has a rotor 15 mounted on the shaft 5. This rotor is provided with an upper shortcircuiting ring 16 and a lower short-circuiting ring 17. The motor stator 3 has upper coil ends 18 extending axially upwardly of the rotor and lower coil ends 19 extending and projecting axially downwardly of the rotor.

The motor shaft 5 has an axial bore 20 into which a first length of tubing 21 is inserted axially. This tubing extends axially downwardly and provides communication between it and the bore of the shaft. The tube is provided with a hollow conical element or lower end portion 22" and is rotationally driven with the shaft to function as a centrifugal oil pump. A transverse opening or passage 23 extends from the shaft bore for lubricating the bearing 4 and three parallel axial passages or bores of reduced diameter 24, 25 and 26 extendaxially upwardly from the main axial bore and terminate within the centrifuging disc 12, as illustrated in the drawing. A branch passage, not shown, for lubricating the crank bearing 14 extends from the bore 24 and another branch lubricating passage, not shown, for applying lubricating oil to the bearing 19 is in communication with the bore 26. Surplus oil not entering the branch passages passes upwardly to the inside of the centrifuging disc 12 and is flung onto the inner wall of the capsule 1 over which it flows back into an oil sump 27 and is cooled in so doing.

According to the invention, a second length of tubing 28 is mounted on the first length of tubing 21 outwardly thereof and spaced therefrom extending axially of the inner or first length of tubing. The outer tubing is provided with a number of circumferentially spaced axially extending depressions 29 which extend radially inwardly defining inwardly-extending projections parallel with the axis of the two tubes to function as spacing elements and mounting the second length of tubing onto the inner or first length of tubing 21.

This outer length of tubing is provided at the lower end thereof with a hollow conical element or lower end portion 30 which terminates in an opening 36 disposed axially spaced upwardly of an opening of the hollow conical element 22. The hollow conical element 39 functions as a second centrifugal pump to deliver oil upwardly by Way of centrifugal action and delivers oil in the space formed between the two tubes.

The second length of tubing 28 is provided with an outwardly extending collar 31 at the upper end thereof by which the tube contacts the lower short-circuiting ring 17 of the motor and defines an annular chamber 32 into which oil is delivered. This annular chamber is in communication with circumferentially disposed and axially extending passages 33 which extend upwardly through the rotor 15 and terminate in a chamber 34 defined by the upper end of a stator coil. The oil entering this chamber is flung outwardly by the upper short-circuiting ring 16 and strikes the upper coil ends 18 and thereby cools them and flows back into the sump 27.

Since the lower opening 35 of the hollow conical element 22 is positioned below the annular opening 36 of the outer hollow conical element 30, the inner pump hollow conical element 22 is capable of delivering oil into its centrifugal pump without interference from the outer conical element.

Those skilled in the art will understand that the embodiment of the invention illustrated can be modified in a number of ways without departing from the basic concepts of the invention. For example, the passages 33 can be used for lubricating the bearing 14. Moreover, the sec ond length of tubing 28 can be secured to the short circuiting ring, to the stator or to the shaft 5 and simply centered around the first length of tubing 21. Furthermore, the outer hollow conical element 30 can, of course, extend downwardly just as far as the inner hollow conical element 22 and, if required, may extend downwardly beyond the inner element.

While a preferred embodiment of the invention has been shown and described, it will be understood that many modifications and changes can be made within the true spirit and scope of the invention.

What we claim and desire to secure by Letters Patent is:

1. In a motor-compressor unit having an oil sump and a vertically disposed driven Shaft having an axial bore, a

centrifugal oil pump comprising a first length of tubing connected to said shaft as an extension of said shaft in communication with said bore and rotationally driven therewith for taking an oil suction from said oil sump, a second length of tubing fixed relative to said first length of tubing disposed circumferentially and axially of said first length of tubing and spaced therefrom defining a second pump suction, a hermetic capsule enclosing said motor-compressor hermetically and defining said oil sump, and means on said second length of tubing mounting said second length of tubing on said first length of tubing and comprising inwardly projecting projections extending axially on said second length of tubing circumferentially spaced thereon bearing against said first length of tubing fixing said second length of tubing thereon.

2. In a motor-compressor unit according to claim 1, in which said projections comprise axial depressions on said second length of tubing extending radially inwardly.

3. In a motor-compressor unit according to claim 1, in which motor-compressor unit comprises an electric motor having a rotor circumferentially of said shaft and fixed thereto, said second length of tubing having an upper end having a collar thereon extending outwardly and disposed engaging said rotor defining jointly therewith an annular chamber in communication with said second length of tubing.

4. In a motor-compressor unit according to claim 3, in which rotor comprises a lower short-circuiting ring, and in which said collar of said second length of tubing bears against an underside of said short-circuiting ring.

5. In a motor-compressor unit according to claim 3, in which said rotor defines axially extending oil flow paths in communication with said chamber for allowing oil flow through said rotor, and a stator circumferentially of said rotor cooled by oil flowing through said flow paths.

6. In a motor-compressor unit having an oil sump and a vertically disposed motor shaft for driving the compressor of said unit, said shaft having an axial bore, a first centrifugal pump comprising a first tube connected to said shaft in communication with said bore, said first inner tube having a lower end conical portion disposed in said oil sump for taking a suction therefrom for delivering oil into said axial bore for distribution therefrom, and asecond centrifugal pump comprising a second outer tube disposed circumferentially outwardly of said inner tube and extending axially thereof and spaced outwardly therefrom, said outer tube having a lower end conical portion disposed in said oil sump for taking an oil suction from said sump and delivering oil in a space defined between the inner and outer tubes, and means in communication with said space for distribution of oil therefrom for cooling.

7. In a motor-compressor unit according to claim 6, in which each of said conical portions has an opening, and in which the openings of said conical portions are axially spaced from each other.

8. In a motor-compressor unit according to claim 7, in which the inner conical portion is disposed lower in said sump and extends outwardly of the opening of said outer conical portion.

References Cited UNITED STATES PATENTS 2,673,075 3/1954 Borck 103-101UX 3,253,776 5/1966 Parker 230206 3,410,478 11/ 1968 Geisenhaver 230206 ROBERT M. WALKER, Primary Examiner 

